Yarn heat treatment apparatus



Jan. 14, 1964 H. CROUZET 3,117,361

YARN HEAT TREATMENT APPARATUS Filed Feb. 11, 1960 FIG. Q

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HENRI CROUZET United States Patent 3,117,361 YARN HEAT TREATMENT APPARATUS Henri Crouzet, Roanne, Loire, France, assignor to Monlinage & Retorderie de Chavanoz, Chavanoz, France, a limited-liability company of France Filed Feb. 11, 1960, Ser. No. 8,046 2 Claims. (CI. 28-62) This invention relates to the thermal treatment of linearly moving yarns, and more particularly to an improved thermal treating apparatus and method.

The continuous thermal treatment of thermoplastic filaments necessitates the application of extremely precise and constant temperatures.

On the other hand, the energy consumption for the heating makes up a considerable proportion of the cost, and all the systems have therefore been designed to obtain low consumption by the utilization of an eliective thermal insulation.

In such apparatus, since the dispersion of heat is low, any too sudden addition of calories, whether the elements concerned have high or low thermal inertia, results in a substantial temperature rise, because, by reason of the time of transmission, the temperature continues to rise for some time after the cessation of the emission of current controlled by a regulating device, and conversely it continues to fall after the re-starting for the same reasons, so that it is very difficult to keep within the desired margin.

In order to keep within the desired margin, the heating has been effected either by controlling the voltage and current and adjusting it in such manner as to produce a constant temperature by equilibrium between the addition of calories, which is proportional to PR, and the losses through the insulation and the treated filament, or by a voltage regulation on an all-or-little basis, of which the all and the little encompass with very close approximation the voltage corresponding to the desired equilibrium temperature.

Regardless of whether the heating is etlected by contact or by means of an ambient medium, such devices operate v well when the quantity of heat carried away by the filament is negligible by reason of the low count of the filament and the low speed employed.

However, the operation of these prior apparatus and methods is not entirely satisfactory when treating fila ments of increasingly high counts and increasingly high speed, since the quantity of calories carried away by the filament is no longer negligible, and the temperature of the heating element consequently varies materially in accordance with the speed at which the filament is traveling and in accordance with its count.

Thus, for example, with an electric heating device controlled by voltage adjustment, if the temperature is 220 C. when no filament is traveling through, this temperature will fall to 210 C., for example, when a filament of considerable count is passed through. If the voltage is adjusted to give a temperature of 220 C. when the filament is traveling at normal speed, this temperature will rise to 230 C. when the filament ceases to travel through, and will be progressively restored to 220 C. only some time after the filament has recommenced its travel. In both cases, therefore, the filament will have been treated under incorrect conditions.

The present invention has for its object to obviate this disadvantage.

The invention consists in an arrangement employing a preheating system which, while requiring no precision and being regulated independently of the final heating system, for example by a thermostat, brings the temperature of the filament roughly to a level slightly below the very precise, constant temperature required for the treatment proper.

Since the precision of the temperature of the preheating system is not high, it is then easy to employ an adjusting system acting on an all-or-nothing or all-or-little basis, the voltage of the preheating system being very much higher than the equilibrium voltage, so that a rapid supply of calories is possible should it be necessitated by the speed and the count of the filament.

The two systems, i.e., the preheating system and the compensating system, are mounted one behind the other in the direction of travel of the filament, in such manner that the filament cannot be substantially cooled between the two.

The invention may be carried out in various ways. One preferred means of application comprises an electrical resistance tube which is surrounded at the end at which the filament enters it by an electrical resistance heater coil. The zone within the tube and the resistance coil at the input end of the tube serves as a preheating zone, while the subsequent zone Within the after section of the tube serves as the compensating zone for bringing the yarn temperature to the desired value, within substantially small limits. The resistance coil receives its electrical energy in regulated quantity from a suitable source of E.M.F., this quantity being regulated as by a thermostat as a feedback function of the temperature of the preheat zone in the tube. In order to achieve rapid raising of the temperature in the preheat zone, the volt-amps supplied to this zone during a call for more heat energy thereto is much higher than is necessary to maintain the desired equilibrium temperature in this zone. The electrical energy supplied to the subsequent compensating zone of the tube is separately similarly regulated as by a second thermostat disposed closely adjacent or preferably within a portion of the tube in the compensating zone. Thus, the temperature in the preheating zone may be regulated within fairly wide limits in view of the large quantity of heat energy imparted to the yarn in this zone, while the temperature of the tube and yarn in the compensating zone may be regulated within substantially smaller limits as a result of the consequent smaller quantity of heat energy which is required to be added to the tube and the yarn in the compensating Zone in order to bring the temperature of the yarn up the remaining amount to the desired value after it leaves the preheating zone.

The invention will be more readily understood with reference to the accompanying diagrammatic drawings of one illustrative embodiment according to the invention, in which drawings:

FIGURE 1 is an overall schematic illustration of the device,

FIGURE 2 shows the temperature curve taken along the device of FIGURE 1, and

FIGURES 3 and 4 illustrate as a function of time the temperature curves taken respectively on the preheating element and on the compensating element, respectively.

In FIGURE 1, the numeral 11 represents an electrical resistance tube, the lower preheat zone portion A of which is surrounded by a heating element 13 in the form of an electrical resistance coil having feed terminals 15 and 17, and to the upper compensating zone portion B of which voltage is directly applied between the input terminal 19 and the output terminal 21. The electrical energy supply through 15 and 17 may be suitably regulated by a thermostat system including voltage regulator 23- and rheostat 24 having a detecting element 22 suitably disposed within a portion of the tube 11 in the preheat zone A and connected to voltage regulator 23, While the @166- trical energy supplied through the terminals 19 and 21 may be suitably regulated by a second thermostat system including voltage regulator 25 and rheostat 26 having a etecting element 27 disposed within a portion of the tube 11 in the compensating zone B and connected to voltage regulator 25.

The yarn Y to be treated passes through the interior of the tube 11 in the direction of the arrow.

If, for example, the external ambient temperature is 20 C. and it is desired to treat the yarn Y at 220 C. in a single heating element, the quantity of calories to be supplied to the yarn, with a predetermined speed of the said yarn, would be a function of the difference: 22020=200 C., taking into account the mass of the yarn passing through per unit time and the calorific capacity of the material of which the yarn consists.

In the system according to the invention, that is to say, comprising a combination of two complementary heating systems it is found, in the case of the above-mentioned example of a treatment at 220 C. and under the same conditions of speed of travel of the yarn, count and nature of the said yarn, that: the element 13, if it is adjusted to effect a temperature of 210 C. in the preheat zone A, supplies a quantity of calories corresponding to: 21020=190 C.

The element 11 itself then has to supply only the quantity of calories corresponding to 220 210 =10 C.

Taking into account the fact that the regulated temperature of the element 13 is not precise and may vary, for example, from 205 to 215 C., the quantity of calories to be supplied by the element 11 in the compensating zone B will therefore have to vary, again taking into account the mass of the yarn and its calorific capacity, to efiect a temperature change of from to 15 C., in the zone B, which quantity is negligible in relation to the unavoidable losses through the insulation. 'For the instant example, assuming that approximately the same ratio of error or variance to required temperature change will prevail in the second Zone B as in the initial preheat zone A, this temperature variation is between approximately +0u25 and 0.75 C.

Temperature error x On the other hand, if only the element 11 were used this temperature would have to vary by approximately 10 C.

The curves in FIGURES 2-4 correspond to and illustrate in general schematic form the approximate temperature curves according to the example taken above.

Although the invention has been described in detail in respect of a single preferred embodiment, it will be readily understood by those skilled in the art that the invention is capable of many modifications and improvements within the scope and spirit thereof. For instance, the tube 11 may be rectilinear or curved, or this or the other heating element may take other and different forms, and although the heating is described as electrical and such is preferred, other heat sources may be employed within the broad scope of the invention. Accordingly it will be understood that the invention is not to be limited by the specific disclosed embodiment but only by the scope and spirit of the appended claims.

That which is claimed is:

1. Yarn heat treating apparatus comprising an electrical resistance tube; a first terminal for electrical energy being connected to said tube at a location intermediate the entrance and exit ends of said tube; another terminal for electrical energy being connected to said tube at a location at the exit end of said tube, the portion of the tube defined by said terminals defining a compensating heating zone wherein yarn passed through the tube is treated at a temperature level approximating the desired temperature level for yarn treatment; a low thermal inertia electrical resistance heating coil surrounding the tube between the inlet end of the tube and said first terminal located intermediate the inlet and outlet ends of the tube, said heating coil having a heating input capable of effecting a temperature very substantially higher than the desired temperature level for yarn treatment in the compensating heating Zone in order that rapid temperature changes may be efiected, but controlled to a level below said desired temperature level for yarn treatment; said heating coil and the compensating heating zone being independently and indivdually temperature regulated.

2. The yarn heat treating apparatus of claim 1 wherein the electrical resistance tube is a contact heater.

References Cited in the file of this patent UNITED STATES PATENTS 2,434,35 1

(Corresponding Great Britain Patent No. 850,080, September 28, 1960) 

1. YARN HEAT TREATING APPARATUS COMPRISING AN ELECTRICAL RESISTANCE TUBE; A FIRST TERMINAL FOR ELECTRICAL ENERGY BEING CONNECTED TO SAID TUBE AT A LOCATION INTERMEDIATE THE ENTRANCE AND EXIST ENDS OF SAID TUBE; ANOTHER TERMINALK FOR ELECTRICAL ENERGY BEING CONNECTED TO SAID TUBE AT A LOCATION AT THE EXIT END OF SAID TUBE, THE PORTION OF THE TUBE DEFINED BY SAID TERMINALS DEFINING A COMPENSATING HEATING ZONE WHEREIN YARN PASSED THROUGH THE TUBE IS TREATED AT A TEMPERATURE LEVEL APPROSIMATING THE DESIRED TEMPERATURE LEVEL FOR YARN TREATMENT; A LOW THERMAL INERTIA ELEDFTRICAL RESISTANCE HEATING COIL SURROUNDING THE TUBE BETWEEN THE INLET END OF THE TUBE AND SAID FIRST TERMINAL LOCATED INTERMEDIATE THE INLET AND OUTLET ENDS OF THE TUBE, SAID HEATING COIL HAVING A HEATING INPUT CAPABLE OF EFFECTING A TEMPERATURE VERY SUBSTANTIALLY HIGHER THAN THE DESIRED TEMPERATURE LEVEL FOR YARN TREATMENT IN TEH COMPENSATING HEATING ZONE IN ORDER THAT RAPID TEMPERARTURE CHANGES MAY BE EFFECTED, BUT CONTROLLED TO A LEVEL BELOW SAID DESIRED TEMPERATURE LEVEL FOR YARN TREATMENT; SAID HEATING COIL AND THE COMPENSATING HEATING ZONE BEING INDEPENDENTLY AND INDIVIDUALLY TEMPERATURE REGULATED. 